The invention relates to a method of calling a substation by a central station in a transmission system.
The method is preferably used in a transmission system which serves for the remote reading of electricity meters.
U.S. Pat. No. 5,390,360 sets forth a method of acquiring access rights to a communication channel in a radio frequency communication system, wherein a first unit interrogates a plurality of second units. The first unit receives a command to start the interrogation cycle by way of a communication channel. The first unit then selects a time delay from a group of time delays and transmits in series, when the channel is free, at the end of the selected time delay, an interrogation request at least to all second units of a subgroup from the plurality of second units.
The English Abstract of JP 10051473 A discloses a communication system In which a master station communicates with a plurality of slave stations by way of a two-way communication path.
EP 581 073 A1 is concerned with a cordless telephone system in which one channel out of a plurality of channels is selected and wherein that selected channel is used for the transmission and reception of speech data in a timesharing mode.
The object of the invention is to provide a method of the kind set forth hereinbefore, which permits optimum, parallel and synchronous utilisation of all available communication means for a group of substations so that a central station, by way of communication channels of that group, detects simultaneously and in an optimum fashion data and in particular measurement data of electricity meters, of all associated substations.
In accordance with the invention the specified object is attained by the features recited in the characterising portion of claim 1. Advantageous embodiments of the invention are set forth in the appendant claims.